Chondroitinases are enzymes of bacterial origin which have been described as having value in dissolving the cartilage of herniated discs without disturbing the stabilizing collagen components of those discs.
Examples of chondroitinase enzymes are chondroitinase ABC, which is produced by the bacterium P. vulgaris, and chondroitinase AC, which is produced by A. aurescens. The chondroitinases function by degrading polysaccharide side chains in protein-polysaccharide complexes, without degrading the protein core.
Yamagata et al. describes the purification of the enzyme chondroitinase ABC from extracts of P. vulgaris (Bibliography entry 1). The enzyme selectively degrades the glycosaminoglycans chondroitin-4-sulfate, dermatan sulfate and chondroitin-6-sulfate (also referred to respectively as chondroitin sulfates A, B and C) at pH 8 at higher rates than chondroitin or hyaluronic acid. However, the enzyme did not attack keratosulfate, heparin or heparitin sulfate.
Kikuchi et al. describes the purification of glycosaminoglycan degrading enzymes, such as chondroitinase ABC, by fractionating the enzymes by adsorbing a solution containing the enzymes onto an insoluble sulfated polysaccharide carrier and then desorbing the individual enzymes from the carrier (2).
Brown describes a method for treating intervertebral disc displacement in mammals, including humans, by injecting into the intervertebral disc space effective amounts of a solution containing chondroitinase ABC (3). The chondroitinase ABC was isolated and purified from extracts of P. vulgaris. This native enzyme material functioned to dissolve cartilage, such as herniated spinal discs. Specifically, the enzyme causes the selective chemonucleolysis of the nucleus pulposus which contains proteoglycans and randomly dispersed collagen fibers.
Hageman describes an ophthalmic vitrectomy method for selectively and completely disinserting the ocular vitreous body, epiretinal membranes or fibrocellular membranes from the neural retina, ciliary epithelium and posterior lens surface of the mammalian eye as an adjunct to vitrectomy, by administering to the eye an effective amount of an enzyme which disrupts or degrades chondroitin sulfate proteoglycan localized specifically to sites of vitreoretinal adhesion and thereby permit complete disinsertion of said vitreous body and/or epiretinal membranes (4). The enzyme can be a protease-free glycosaminoglycanase, such as chondroitinase ABC. Hageman utilized chondroitinase ABC obtained from Seikagaku Kogyo Co., Ltd., Tokyo, Japan.
In isolating and purifying the chondroitinase ABC enzyme from the Seikagaku Kogyo material, it was noted that there was a correlation between effective preparations of the chondroitinase in vitrectomy procedures and the presence of a second protein having an apparent molecular weight (by SDS-PAGE) slightly greater than that of the major protein component of chondroitinase ABC. The second protein is now designated the "chondroitinase II", while the major protein component of chondroitinase ABC is referred to as the "chondroitinase I." The chondroitinase I and II proteins are basic proteins at neutral pH, with similar isoelectric points of 8.30-8.45. Separate purification of the chondroitinase I and II forms of the native enzyme revealed that it was the combination of the two proteins that was active in the surgical vitrectomy rather than either of the proteins individually.
Use of the chondroitinase I and II forms of the native enzyme to date has been limited by the small amounts of enzymes obtained from native sources. The production and purification of the native forms of the enzyme has been carried out using fermentations of P. vulgaris in which its substrate has been used as the inducer to initiate production of these forms of the enzyme. A combination of factors, including low levels of synthesis, the cost and availability of the inducer (chondroitin sulfate), and the opportunistically pathogenic nature of P. vulgaris, has resulted in the requirement for a more efficient method of production. In addition, the native forms of the enzyme produced by conventional techniques are subject to degradation by proteases present in the bacterial extract. Therefore, there is a need for methods to isolate and purify a reliable supply of the chondroitinase I and II enzymes free of contaminants in order for the medical applications of the two forms of this enzyme to be evaluated properly and exploited.